JPH06347337A - Temperature detecting circuit - Google Patents

Abstract

PURPOSE:To enable execution of a temperature detecting operation at a lower voltage than a usual one without sacrificing a detection error, in a temperature detecting circuit. CONSTITUTION:This temperature detecting circuit comprises a circuit wherein an element 1 having strong temperature dependence, such as a P-N junction diode or an MOS transistor, is connected to the positive voltage terminal 13 and an element 2 having weak temperature dependence, such as a resistor, is connected to a negative voltage terminal 14 and which is so constructed that a voltage at a node N1 of the two elements 1 and 2 changes in relation to temperature, a circuit wherein an element 3 having weak temperature dependence, such as the resistor, is connected to the positive voltage terminal 13 and an element 4 having strong temperature dependence, such as the diode or the MOS transistor, is connected to the negative voltage terminal 13 and wherein a voltage at a node N2 of the two elements 3 and 4 has the dependence on the temperature being reverse to that of the voltage at the node N1, and a comparator 5 to which the voltages at the nodes N1 and N2 are inputted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature detection circuit, and more particularly to a temperature detection circuit having a detection element whose electrical characteristics change due to temperature change and detecting whether the temperature of a detection portion is above or below a predetermined temperature. Regarding the circuit.

[0002]

2. Description of the Related Art A circuit diagram of an example of a conventional temperature detecting circuit of this type is shown in FIG. Referring to FIG. 3A, in this detection circuit, the element 1 having a strong temperature dependence of electrical characteristics is connected to the positive voltage terminal 13 side, and the element 2 having a weak temperature dependence is connected to the negative voltage terminal 4 side. A detection unit configured to be connected so that the voltage at the connection point N1 of both elements changes with temperature, and a reference voltage generation unit 1 for generating a reference voltage with extremely small temperature change.
0, and a comparator 5 to which the output voltage of the detection unit and the output voltage from the reference voltage generation unit 10 are input.
To further increase the detection power for temperature, refer to FIG.
As in the other example of the conventional temperature detection circuit shown in FIG. 3, a plurality of elements having a strong temperature dependency (two elements, 11 and 12 in this case) are connected in series.

In a semiconductor integrated circuit, a pn junction diode is a typical element having a strong temperature dependency. 3 (b) and 4 (b) are shown in FIGS. 3 (a) and 4 (a) using a diode as an element having a strong temperature dependence and a low antibody as an element having a weak temperature dependence. The temperature characteristics of the input voltage of the comparator 5 and the logical output value of the comparator 5 are shown for each case where the detection circuit is realized.

[0004]

When the temperature detection circuit shown in FIG. 3A is realized by a semiconductor integrated circuit, the temperature coefficient of the input voltage to the positive input terminal of the comparator 5 is in the order of the element (diode) 1. Almost determined by the temperature coefficient of directional voltage, at most 2
Only mV / ° C can be obtained. Therefore, a minute change in the reference voltage has a great influence on the detected temperature. That is, the temperature detection error increases.

On the other hand, if the configuration shown in FIG. 4A is used and the change in the input voltage to the comparator 5 with respect to the temperature is increased, the detection error due to the change in the reference voltage can be reduced. For example, when the diode has two stages, the temperature coefficient of the input voltage to the comparator 5 is about 4 mV / ° C., so that the reference voltage has less influence on the detected temperature. However, in this case, if the voltage supplied to the detection unit (voltage between the positive voltage terminal 13 and the negative voltage terminal 14) is left unchanged, the input voltage of the comparator 5 is equal to the forward voltage of the diode. Since the temperature becomes lower, the detection temperature lowers. In order to eliminate the decrease in the detected temperature and detect the same temperature as that of the detection circuit shown in FIG. 3A, the supply voltage to the detection unit must be set to about 1.4V or higher. For this reason, it becomes difficult to realize a low-voltage drive detection circuit using, for example, a dry battery, using a circuit with a small detection error as shown in FIG.

Therefore, an object of the present invention is to provide a temperature detection circuit which has a smaller detection error than the conventional temperature detection circuit and can be driven at a low voltage.

[0007]

The temperature detection circuit of the present invention comprises at least one element whose electrical characteristic changes with temperature, and is determined by the electrical characteristic of this element and the supply voltage supplied from the outside. A first circuit configured so that the output voltage exhibits temperature dependence, and at least one element whose electrical characteristic changes with temperature, and an output determined by the electrical characteristic of the element and the supply voltage A second voltage arranged to exhibit a temperature dependence opposite to that of the output voltage of the first circuit;
And a comparator which receives the output voltage of the first circuit and the output voltage of the second circuit as inputs.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1A is a circuit diagram of the first embodiment of the present invention. With reference to FIG. 1A, in this embodiment, two pn junction diodes 1 and 4 are used as elements having a strong negative temperature dependence, and two resistors 2 and 3 are used as elements having a weak temperature dependence. ing. That is, by connecting the diode 1 to the positive voltage terminal 13 side and the resistor 2 to the negative voltage terminal 14 side, the voltage at the connection point N1 of both elements has a characteristic of approximately 2 mV / ° C. with respect to temperature. And the resistor 3 is connected to the positive voltage terminal 13 side and the diode 4 is connected to the negative voltage terminal 14 side, and the voltage at the connection point N2 of both elements changes with temperature at about -2 mV / ° C. And the voltage at the connection point N1 (2m
V / ° C.) and the voltage of the connection point N2 (−2 mV / ° C.). Since the voltage between the input terminals of the comparator 5 receives the voltages at the connection points N1 and N2,
As shown in FIG. 1 (b), it has a temperature dependence of substantially 4 mV / ° C. In FIG. 1A, a voltage of 0.9 V is applied between the positive voltage terminal 13 and the negative voltage terminal 14, and the forward voltage of the diode at 25 ° C. is 0.65 V.
It was. In this case, when the temperature of the diodes 1 and 4 reaches 125 ° C (at the time of 100 ° C rise), the diode 1
And the forward voltage of 4 becomes 0.45V, the connection point N
The voltage at 1 and the voltage at the connection point N2 are equal to 0.45 V and are equal. Therefore, above this temperature, as shown in FIG. 1B, the magnitude relation of the voltages entering the comparator 5 from the connection points N1 and N2 is inverted, and the level of the output terminal 15 is switched from low to high. That is, in the conventional temperature detection circuit shown in FIG. 4B, in order to detect the temperature of 125 ° C., the positive voltage terminal 1
While it was necessary to supply a voltage of 1.4 V between the No. 3 and the negative voltage terminal 14, according to the present embodiment, a low supply voltage of 0.9 V while maintaining the detection error at the same level as the conventional one. It will be possible to detect that the temperature is 125 ° C. or higher.

Next, two embodiments of the present invention will be described. FIG. 2A is a circuit diagram of the second embodiment of the present invention. With reference to FIG. 2A, in this embodiment, two n-channel MOS transistors 6 and 7 are used as elements having a strong negative temperature dependence, and two resistors 2 and 3 are used as elements having a weak temperature dependence. Is used. That is, by connecting the MOS transistor 6 to the positive voltage terminal 13 side and the resistor 2 to the negative voltage terminal 14 side, the connection point N of both elements is
A circuit in which the voltage of 1 has a characteristic of approximately 5 mV / ° C with respect to temperature, and a resistor 3 is connected to the positive voltage terminal 13 side and M
By connecting the OS transistor 7 to the negative voltage terminal 14 side, the voltage at the connection point N2 of both elements is approximately -5 mV / temperature.
Circuit that has characteristics that change with ° C and connection point N1
Voltage (5 mV / ° C) and the voltage at the connection point N2 (-5 mV /
C) and a comparator 5 which receives as input. Since the voltage between the input terminals of the comparator 5 receives the voltages at the connection points N1 and N2, it has a temperature characteristic of substantially about 10 mV / ° C. In this structure, the voltage between the source and drain electrodes of the n-channel MOS transistor at 25 ° C. is 0.8V. Here, when the temperature of the two MOS transistors 6 and 7 rises 100 ° C. to 125 ° C., the source-drain voltage of each MOS transistor becomes 0.3V. At this time, if a voltage of 0.6 V is applied between the positive voltage terminal 13 and the negative voltage terminal 14, the voltage at the connection point N1 becomes equal to the voltage at the connection point N2. That is, according to this embodiment, by making the substantial temperature coefficient of the input voltage of the comparator 5 larger than that in the first embodiment, as shown in FIG. Only 0.6V supply voltage will be needed to detect temperature.

[0010]

As described above, the temperature detecting circuit of the present invention is provided with at least one or more elements whose electrical characteristics change with temperature, and the first output voltage is temperature dependent. And at least one element whose electrical characteristics change with temperature, the output voltage of which has a temperature dependence opposite to that of the output voltage of the first circuit. 2 circuits and 1st
And a comparator that receives the output voltage of the second circuit and the output voltage of the second circuit.

As a result, according to the present invention, it is possible to provide a low power consumption temperature detection circuit that can operate at a lower voltage than before without sacrificing detection error.

[Brief description of drawings]

FIG. 1A is a circuit diagram of a first embodiment of the present invention. Diagram (b) is a diagram showing how the input voltage and the logic output in the comparator in diagram (a) change with temperature.

FIG. 2A is a circuit diagram of a second embodiment of the present invention. Diagram (b) is a diagram showing how the input voltage and the logic output in the comparator in diagram (a) change with temperature.

FIG. 3A is a circuit diagram of an example of a conventional temperature detection circuit. Diagram (b) is a diagram showing how the input voltage and the logic output in the comparator in diagram (a) change with temperature.

FIG. 4A is a circuit diagram of another example of a conventional temperature detection circuit. Diagram (b) is a diagram showing how the input voltage and the logic output in the comparator in diagram (a) change with temperature.

[Explanation of symbols]

 1, 2, 3, 4, 6, 7, 11, 12 Element 5 Comparator 10 Reference voltage generator 13 Positive voltage terminal 14 Negative voltage terminal 15 Output terminal

Claims (4)

[Claims] 1. A device comprising at least one element whose electrical characteristics change with temperature, and an output voltage which is determined by the electrical characteristics of the element and an externally supplied voltage is temperature-dependent. A first circuit and at least one element whose electrical characteristic changes with temperature, and an output voltage determined by the electrical characteristic of the element and the supply voltage is the output voltage of the first circuit. A second circuit configured to exhibit a temperature dependence opposite to that of, and a comparator having an output voltage of the first circuit and an output voltage of the second circuit as inputs. A temperature detecting circuit comprising. 2. A first element having a strong temperature dependence of electrical characteristics is arranged on the positive voltage terminal side, and a second element having a weak temperature dependence of electric characteristics is arranged on the negative voltage terminal side. The first element and the second element are connected between a positive voltage terminal and the negative voltage terminal.
A fourth circuit in which a first circuit in which the above-mentioned element is connected in series and a third element whose electric characteristic temperature dependence is weak are arranged on the side of the positive voltage terminal, and whose electric characteristic temperature dependence is strong. A second circuit in which the third element and the fourth element are connected in series between the positive voltage terminal and the negative voltage terminal, and the first circuit is disposed on the negative voltage terminal side. A temperature detector, comprising: a comparator having a voltage at a series connection point of the two elements of the circuit and a voltage at a series connection point of the two elements of the second circuit as inputs. 3. The temperature detection circuit according to claim 2, wherein a pn junction diode is used as each of the first element and the fourth element whose electric characteristics have a strong temperature dependence, and A low temperature antibody is used as the weak second element and the weak third element. 4. The temperature detection circuit according to claim 2, wherein a drain electrode and a gate electrode are connected to form a diode connection as the first element and the fourth element having high temperature dependence of electrical characteristics. A temperature detecting circuit using a channel type MOS transistor, wherein a low antibody is used as the second element and the third element having weak temperature dependence of electrical characteristics.